Electronic switching system
In telecommunications, an electronic switching system is a telephone switch that uses solid-state electronics, such as digital electronics and computer
The generations of telephone switches before the advent of electronic switching in the 1950s used purely electro-mechanical relay systems and analog voice paths. These early machines typically utilized the step-by-step technique. The first generation of electronic switching systems in the 1960s were not entirely digital in nature, but used reed relay-operated metallic paths or crossbar switches operated by stored program control systems.
First announced in 1955, the first customer trial installation of an all-electronic central office commenced in Morris, Illinois in November 1960 by Bell Laboratories. The first large-scale electronic switching system was the Number One Electronic Switching System of the Bell System, cut over in Succasunna, New Jersey, in May 1965.
Just three years later, in September 1968, Britain's Post Office opened the world's first all-digital pulse-code modulation exchange named Empress. Other nations vying to reach the forefront of technical innovation would adopt metal–oxide–semiconductor and PCM technologies to make their own transitions from analog to digital telephony throughout the 1970s. Later electronic switching systems implemented the digital representation of the electrical audio signals on subscriber loops by digitizing the analog signals and processing the resulting data for transmission between central offices. Time-division multiplexing technology permitted the simultaneous transmission of multiple telephone calls on a single wire connection between central offices or other electronic switches, resulting in dramatic capacity improvements of the telephone network.
With the advances of digital electronics starting in the 1960s telephone switches employed semiconductor device components in increasing measure.
In the late 20th century most telephone exchanges without TDM processing were eliminated and the term electronic switching system became largely a historical distinction for the older SPC systems.